Due to the continuous increase in magnetic recording densities, small distance head-disk, and increase in the rotation speed of the disk, conventional lubricants are facing several obstacles, such as weak durability, heavy lubricant pickup, and uncontrollable friction. The media surface must be well protected from damage due to sporadic contacts with the disk head when it flies over the disk. Therefore, hard disk media with good wear durability is very important to ensure the reliability of a hard disk drive and to prevent the disk from damage caused by poor performance of the lubricant.
Typically, a very thin lubricant film with 1-2 nm thickness is deposited onto a hard disk surface and the lubricant film ought to provide sufficient protection to the hard disk surface. When the disk head flies over an area of the disk surface, a portion of the lubricant film is replaced and lubricant in close proximity flows back to the lubricant-depleted area in a certain time period to cover the zone that the lubricant coverage is depleted before the disk head flies over the same area again. It thus requires lubricant to have sufficient mobility which is capable of repairing the damaged area within an allowable time period in order to prevent disk failure.
Lubricants with poor mobility need a longer time to flow into the lubricant-depleted area. As a result, there is a possibility that the disk head flies back to the lubricant-depleted area which is not sufficiently covered up by the adjacent lubricant, thus resulting in disk failure. In contrast, high mobility leads to fast replenishment of the lubricants. In theory, lubricants with sufficiently high surface mobility are able to effectively prevent damage of the disk. Enhancement of lubricant surface mobility may be achieved by designing a lubricant with either a relatively low molecular weight or with terminal groups that have weak interaction with the disk surface.
In any case, both alternatives pose problems. For example, on one hand, a lubricant with a low molecular weight usually has relatively high volatility and subsequently results in fast evaporative loss during a long term usage. On the other hand, the weak interaction between the lubricant and the hard disk surface makes it difficult for the lubricant to bond to the hard surface, leading to poor bonding of lubricant to the disk surface and inevitably causing disk damage.
Therefore, there remains a need to provide lubricants that overcomes, or at least alleviates, the above problems.